I’ve done some workshops for non-programmers recently and I’ve been using the Flickr feeds (https://www.flickr.com/services/feeds/) as a simple demonstration of APIs – the workshop uses a Google Spreadsheet to interact with the feeds – modifying parameters in the call and extracting information from the results.

Perhaps a bit limited, but I think good for a quick introduction and enough of the basic concepts to be interesting.

(this particular workshop was for staff at the British Library and is based on a previous workshop I did documented at http://www.meanboyfriend.com/overdue_ideas/2013/02/introduction-to-apis/ – but unfortunately the original API I used in that example no longer works and I haven’t had time to write up the exercise modified to use the Flickr API yet)